1. Field of the Invention
The present invention relates to traffic management apparatus and a method of routing network traffic comprising requests to a plurality of server computers, and in particular the routing of requests based their attributes.
2. Description of the Related Art
The provision of data over the Internet is well established, where a client computer, possibly using a web browser, makes a request for data to be served from a server computer. In recent years, the size and bandwidth requirement of data requested by clients has increased, and on occasion demand for particular types of data, such as a highly popular web page, can be very high. Consequently, it is necessary for similar data to be served from a plurality of web servers in order for the demand to be satisfied.
In order to optimise the availability of server resources, it is known to provide additional functionality within a service providers network so as to route network traffic to one of a plurality of servers, a process known as load balancing. Load balancing systems are described in United Kingdom patent publication numbers 2 413 868 B and 2 414 136 B, both assigned to the present applicant. In these implementations, load balancing is provided by traffic management systems.
In addition to providing load balancing of network traffic across a plurality of servers, it is known in very high load situations to provide more than one traffic management system, each sharing the same Internet Protocol (IP) address. Such a system is described in European patent publication number 2 288 111 A, also assigned to the present applicant.
A problem associated with such implementations is encountered when one traffic manager fails, either due to a systems crash or hardware failure, for example. Certain types of connections from clients are persistent and require consistent routing of network traffic (comprising requests) to the same server. If a traffic manager responsible for routing network traffic belonging to a particular connection goes offline, then the details of which server the network traffic should be routed to are lost and may cause loss of connectivity.